The disc material won't rust but the pressure plate and flywheel will. The rust mingles with and grips the friction material, much like a rusty can sticks to a damp piece of cardboard over time. Sometimes you can break the clutch loose if you hold the clutch pedal down and try to start it or drive it with the brake applied. Otherwise you'll have to go ahead and pull the trans to separate pressure plate, disc and flywheel.

Some recommend to block the clutch pedal or fork in the released position if the vehicle won't be driven for awhile, though this might be hard on the pressure plate spring.

Happy Motoring, Mark

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DrDKW